Most known metro wavelength division multiplexed (WDM) networks are based on optical rings that include various types of optical add-drop multiplexers (OADMs), which perform drop and add functions through an optical filtering operation. Most metro WDM networks are substantially based on optical circuit switching, and the granularity is wavelength, however optical burst switching (in which a number of data packets are assembled into a data burst for transmission) based metro WDM networks have recently emerged based on agile utilization of optical tunable sources and fixed wavelength receivers.
Reconfigurable Optical Add Drop Multiplexer (ROADM) nodes in ring networks have been developed to transport transit data traffic travelling on multiple wavelength signals without optical-electrical-optical (OEO) conversion, which switch only data traffic addressed to a specific node. When a new node is added to the network, new transponders have to be included in each of the existing nodes, since each wavelength is dedicated for communication to a specific node.
Ring network nodes based on optical burst switching have been proposed [Ian M. White et al, “A Summary of the HORNET Project: A Next-Generation Metropolitan Area Network”, IEEE JSAC, Vol. 21, N. 9, November 2003], including the Matisse Networks EtherBurst node which comprises a single fast tunable optical transmitter and a fixed wavelength receiver to drop traffic addressed to that node. Optical burst switching channels are implemented by rapidly tuning the wavelength of the laser to the wavelength of a destination node. Medium access control (also known as Media Access Control) (MAC) protocols are used to assign resources among a number of such nodes forming a ring network.